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EPDM Synthetic Rubber Solar Collectors are not Compatible with Swimming Pool Chemistry

Almost every solar pool heating dealer that has any lengthy experience has run into the phenomenon of black goo, dust or particles oozing out of an EPDM synthetic rubber solar collector, making a mess of the pool. Hot Sun gets calls on this almost every week. Granted, many of these systems are older. Many times the customers aren't too upset because they got 6 or 8 years service out of their solar heater and this has been good service. Some have even lasted 20 years or more. This is a powerful defense for the supplier and besides, the systems have usually paid for themselves many times over. No harm no foul. At Hot Sun we have always used thermo plastic based materials with zero risk of this kind of breakdown but during our technology development we did stray toward EPDM and we were punished. Selling epdm knowing there is a problem with chemistry puts solar companies on a slippery slope. Why not just tell people that 80 sq ft of solar collector will raise pool temp 10 degrees? Hmmm. That's what it says right on the box of the 4x20 at the pool store.

The rumors and stories on the epdm breakdown topic have circulated by word of mouth since long before the internet age. Dory Mowlavi (now retired) , owner of Solartrope Supply Corp, in Orange CA announced to us in 1989 that the epdm rubber tubing breaks down sometimes so his suppliers had switched materials to "Santoprene". A year later the story was that Santoprene broke down even quicker. Oops. Since writing this article on this issue we've learned from people in the industry at that time that there wasn't a lawsuit. There was a payout but it didn't come close to fully compensating those that put their good name behind epdm.

Solaroll was the biggest and most prolific product of this kind. It has now resurfaced in South Africa and claims a long history (since 1977) in the business.

Tom Lane is a famous solar pool heating contractor in Central Florida. His recently published book, "Solar Hot Water Systems Lessons learned 1977 to Today" chronicles his experience in this industry. He flat out states on page 183. "WARNING: DO NOT BUY RUBBER MAT POOL COLLECTORS (EPDM RUBBER) THEY CANNOT STAND UP TO POOL CHEMICALS"

Hopefully Tom Lane won't mind me quoting that line from his book if I provide a link here to his web site where you can buy it yourself. Its an awesome chronicle of his life's experience with this technology.

In 2003 Hot Sun got involved with an EPDM product made in Canada. Hot Sun knew about "black pool" and was afraid of it. We didn't want to use epdm but its tough and its cheap and this company had been using it for 27 years when we first started selling their product. We displayed the system at the Western Pool and Spa Show one year and we spent 3 days with the manufacturer. Ken Wright, Hot Sun's president presented them with a non-epdm, high temperature flexible plastic version of the fin tubing. They couldn't understand why Mr Wright would want to sell a non-epdm collector material. They admitted they'd run into the issue in the past but it was always the fault of unusually high iron or other minerals in the pool water. They weren't technical people but this is what their scientists had concluded. Hot Sun had just finished an installation in North Carolina at a commercial pool. The system was 2000 sq ft. None of the known factors like water sitting stagnant in the collectors in summer were applicable to this situation so we thought it would be OK.

Fast forward only 3 years. The tubing began to break down and shoot particles of black goo into the pool only 3 years after installation. Hot Sun knew exactly what had happened. After only 3 years on a large commercial installation we had to offer compensation. The manufacturer played dumb of course but we presented them with the evidence presented here on this web page in an effort to motivate them to do the right thing. They helped pay for a replacement system. There was no warranty because warranties don't provide refunds 3 years after the fact. They only offer replacement but if the replacement is as flawed as the original what good is it? We had to replace EPDM with our plastic based system.

Here is some of the evidence. Now that we have published this many customers, solar dealers, pool servicemen and the people directly affected by the fallout around 1990 have come forward to talk about it. We've even had to guarantee our product would not be affected by chlorine the same way in order to satisfy a health department in one municipality. They had a record of complaints of this phenomenon in public facilities! Its a very well known issue but until we took the step to publicize it you couldn't find any evidence that any of this ever happened. Many companies still sell epdm solar panels today. To be fair in some cases it is a fairly minor issue that does not occur in every case and it can often be dealt with in a way that does not require a full collector replacement. At Hot Sun we want no part of any of this. We have the luxury of technology that does not suffer this same problem.

This is a document detailing the effect of chlorine on epdm when used as a tank liner. This is just tap water never mind pool water and this is all low temperature.

Look at what the seal industry has had to go through when dealing with sealing water that is chlorinated. This document shows EPDM seals breaking down in chlorinated water and Parker's take on what the cause is. The factors at play are much worse in a swimming pool application and these chloramine resistant rubbers are far too expensive to make solar panels out of. Besides they only reduce the effect and the effect can be much worse in a swimming pool.

This paper studied the breakdown of epdm in seals in Japan's city water system and determined the actual mechanism at work.

This is a list of materials and their compatibility with various liquids. Note that epdm is specifically not recommended for use with chlorinated water. Note aklso we're only talking drinking water chlorine levels and no elevated temperatures.

This set of photos shows the Franklin Health and Fitness Center's Enersol system and the breakdown of the solar collector. We have an affidavit on file from the owner of the Health club as well as from the contractor who installed the replacement system and we kept some of the collectors just in case anyone wants to challenge us on these facts.

In the pool industry and the solar pool heating industry its all about sales. Its not about technology so the analyses of this issue is based on rumor. The science simply hasn't been applied. The Franklin Health and Fitness Center fiasco didn't stop us from our pursuit of a rubber solution that didn't break down and there has been a lot of work done toward this goal by companies like Parker Seals. The solutions are proprietary and expensive. Our favorite epdm extruder could copy the "Panacea" made by others but again it is very expensive and given the high heat and the high chlorine doses there is still no guarantee breakdown would not occur. We do have several pallets of this in stock and we can supply an epdm solar collector that will outlast all others but we can't guarantee that for 25 years like we can with our regular Powerstrip.

So now that this is all published right here what is a consumer to do knowing company X sells an epdm solar collector but claims these issues are behind them. The answer is simple. Just look at the warranty from this perspective. If it isn't specifically covered for this issue, then its not going to be covered if there is an event. Its not a manufacturing defect after all. There are standard remedies in the industry. Filter the return from solar and change the filter every season. Another remedy is to dump the slug of polluted water down the drain at the start of a season. You see, normally the black stuff doesn't come off the inside of the collector all the time. Usually water has to sit in the collector for a while and heat up before the reaction re-occurs. At Franklin, we didn't experience any of those things. It just started oozing black particles.

More evidence of a sort. This was a worldwide problem. EPDM was the standard solar pool heating material 40 years ago. In Australia this problem occurred as well. The solution there was to switch to a plastic based alternative. For years Hot Sun aligned ourselves with various Aussie competitors in the fight against EPDM competitors. Hot Sun has the solution to all this. That puts us in a position where we can be honest.

There are many papers on the subject. We know the effect is caused by the chloramines. These are the combined chlorines created when free chlorine disinfects organic matter. You can't avoid this if you're using chlorine to sanitize the water. Heat is a big factor in breakdown as well. You can't avoid the heat of a black thing in the sun with the pool up to temperature. What you can do is avoid the use of epdm by challenging the supplier to specifically protect you against this phenomenon for 25 years as you see in the Powerstrip warranty.

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We believe we are the only solar company to ever attempt to publish these facts. We're exposing ourselves to a lawsuit here so we have to be very careful and we have to collect as much evidence from as many people as we can, otherwise we can't publish any of this.

As a footnote, we've sold two other large commercial solar pool heating systems in North Carolina since we replaced the one above using it as a reference. It always pays to behave with integrity even if your only objective is to make money. We attribute all of this to too much focus on sales and marketing and too little concern for technology. Engineers are absent in the pool industry. They need to take charge more often. Ken Wright has a mechancial engineering degree from UBC 1984.

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